In-Plane Stiffness of Hybrid Steel–Cross-Laminated Timber Floor Diaphragms

Abstract

The use of hybrid structural systems formed by combining wood with other materials provides engineers with a wide range of solutions to satisfy code requirements for mid- and possibly high-rise buildings. Hybrid wood-based systems include a wide range of construction methods and different levels of integration of materials and components. The research discussed in this paper presents an innovative hybrid timber-steel solution for floor diaphragms developed by joining cross-laminated timber panels with cold-formed customized steel beams. The repeatable floor unit is prefabricated off site and then fastened on site using preloaded bolts and self-tapping screws. The paper discusses the in-plane stiffness of the floor and the distribution of the horizontal loads to the shear walls. A numerical model was developed with its input parameters calibrated from full-scale experimental tests. The effects of connections and element arrangement, load and constraint conditions, the relative stiffness of shear walls and their spacing, as well as the floor aspect ratio on the load-displacement response of floors has been investigated. The findings allow engineers to find the fundamental design parameters and evaluate their role in the diaphragmatic behavior of floors. In particular, unfavorable layouts for the shear walls must be avoided in order to prevent an excessive in-plane deformation of the buildings.